Propeller for aeroplanes



March 17, 1931. BOCKSRUKER 1,797,068

- PROPE'LLER FOR AEROPLANES Filed June 27, 1927 2 Sheets-Sheet l BY v ATTORNEY March 17, 1931. BQCKSRUKER 1,797,068

PROPELLER FOR AEROPLANES Filed June 27, 19 27 2 Sheets-Sheet-Z NNNNNN OR Patented Mar. 17, 1931- ALEXANDER nooxsiwxnn, or MILWAUKEE, WISCONSIN PROPELLER FOR AEROPLANES Application filed June 27, 1927. Serial No. 201,879.

The present invention relates to propellers designed with special reference. to use on aeroplanes. The object of the'invention is to increase the speed of the aeroplane and to increase its lifting power.

In carrying out theinvention I provide a plurality of propeller blades integral with a central'hub, the several blades being substantially elliptical incross section and having their front edge straight and their rear edge circular, the hub end overlapping the axis of rotation and said blades being of varying depth gradually approaching a plane at their outer ends and forming a slope of 45 at their inner terminus to facilitate the air compression which may have an intake near the axis and afford a translative motion to the plane. The blades are of very substantial construction and'are formed from a light and very tenacious wood suchas black walnut, or from tenacious light steel. Each of the blades is of varying depths from the inner end to their tip, the cross sect onal shape thereof presenting an arcuate outer face at the hub, which gradually decreases to the tip, and an inclined inner face gradually decreasing from the hub to the tip, with a flange on the curved or circular edge of the blade, having its outer side curved in a gradually increased degree ,from the hub outward, while its inner side is inclined toward the inner face of the blade and disposed at an obtuse angle with respect thereto, said flange being tapered and terminating adjacent the outer end of the blade and such arran ement presenting a construction that is capa le of compressing air and diverting the same centrifuge-11y. 4

The invention therefore comprises in its broadest phase a propeller having a plurality of elliptically concave blades which may overlap each other in a case of six blades at a hub of considerable diameter and having a discharge area beyond the axis of rotation. It comprises other features of novelty which will be more fully hereinafter described and will be definitely indicated in the appended claim.

In the accompanying drawings which illustrate' the invention:

Figure 1 is an elevation .of a propeller having six blades embodying my improvements. Figure 2 is a side elevation-of the same.

Figures 3, 4, 5, 6 and 7 represent enlarged cross sections of the blades at progressive distances from the axis, Figure 3 being taken near the tip on the transverse plane 33 of Figure 1, Figure 4 on the plane 44, Figure 5 on the plane 5-5, Figure 6 on'the plane 66, and Figure 7 on the plane 7-7 of Figure 1. I

Figure 8 is a cross sectional view of the hub and part of one of the propelling blades.

Referring now in detail to the drawings, I have shown in the design illustrated a propeller having six blades. However, 'the number of blades may vary as it might well be adapted for three blades 120 apart, or

other number symmetrically distributed.

The number of blades may vary with the design of the plane and may be 3, 4 or 6 with speeds 2100 to 3000 R. P. M. These blades are shown at 1, 1a etc., and are symmetrically mounted 60 apart in this particular case, forming a solid part of a large-hub 2. The material of which the integral structure is made may be of a light strong wood as American black walnut or of a tenacious metal such as annealed carbon steel. The hub which is circular is recessed but has a closed front wall with a bearing sleeve centrally arranged therethrough, and in the recess there is pro vided a plurality of radially arranged walls 3 extending from the sleeve to the peripheral wall of the hub, and connecting webs 4 are provided for these radial walls, the webs being disposed midway between the sleeve and the peripheral wall as best shown in Figure 1 of the drawings and are adapted to reinforce the walls of the hub as will be apparent. O symmetrically distributed over the honeycombed part of the hub are a plurality of bolt holes to accommodate 5, 5a, by which a conical cap 6 may be rigidl secured to form a minimum resistance to wind, this cap serving to cover a plurality of nuts 7, 7 a by which the propeller may be securely splined to a drive shaft 8. The hub is provided with an annular fiangepxtending from its front wall for the purpose of accommodating the cap as best shown in Figure 8. The blades of the for the air that propeller are formed with the hub and extend therefrom in spiral formation, and each of the blades is formed with a longitudinally straight edge 90; and a longitudinal curved edge 10a. The blades are also of graduallyvarying width, with a transverse outwardly curved or convexed face 10 and a straight inclined inner or rear face merging at one side into the straight edge 9, such width being indicated in Figures 3 to 7 inclusive, and decreasing from the hub to the tip 11, with a flange providing with the straight face a scoop shaped arrangement to form pockets guradually tapers to the tip 11 as suggested in l igure 1, the bottom wall of the pocket having a smooth contour following the curvature of the blade, the inner section of which at the hub forms what may be regarded as a subwing and the flange which is indicated by the reference numeral 12 being formed at an obtuse angle with respect to c the face 9. The pocket in the forward side of the blade is of varying depth from theoretical zero but practical 5 2' radial inlet edge of blade, to a maximum somewhat beyond the center of each particular circular blade section. The maximum thickness of any circular section in question is nearer the inclination than to the radial inlet edge marked 11 on the drawing, thus supporting the center of forces. The walls of the subwings are strongly bonded where the recessed walls intersect at 20 and 45 and where the elliptical curves intersect the hub. The wing recesses are elliptical in cross section with vary -,1ng coordinate axes increasing to the maximum equalto the hub width and vanishing at the tip.

It willbe apparent from this construction that when the engine is running at full speed in its takeofi from a station the cups will form a pocket in which air will be compressed and driven radially and centrifugally, creating a forward moment and a definite lifting moment to the aeroplane. This lifting moment will be zero at the tip of the blades reaching its maximum at of the blade, decreasing to zero at the hub. The relative pressures will be modified according to the conformation of the cup in the wings, but is deepest near the hub, determining a strong air compression'at the point I call the subwing, driving with augmenting force through the connected main wing to the outer tip with a strong propulsive mo ment which when the aviatorap'plies the helm will resolve itself into a strong lifting moment. The conical cap 6 covering the front of the hub diverts the wind currents radially to the subwings for the benefit of the radial intake edge 11. The walled re cesses of the hub and above the elliptically recessed wings are areas of low air pressure,

I have described the invention as applied to a propeller having six blades. lit is apparent, however, that any desired number of blades may be used adapted to difi'erent propeller speeds, for, instance, they may beset 120 apart instead of 60 as in the present illustration, and a higher angular velocity would be required with fewer blades; the coordinate of the cross section will vary and modify the hub width.

While my invention is primarily intended for use in aeroplanes, the construction is adapted for propellers of other types, as for use on water propellers.

Having thus described my invention, what ll claim as new and desire to secure by Letters Patent is:

In a propeller, a hub circular in formation and being provided with a recess, a front wall included in said hub, a bearing sleeve extending through the front wall and centrally arranged with respect to said hub, walls radiating from the bearing sleeve and extending between the latter vand the peripheral wall of the hub, webs connecting the radially extending walls and disposed midway between-the sleeve and peripheral wall, an annular flange extending forwardly from the front wall, a conical cap received by the annular flange, means for securing the cap about said flange and passed through the front wall, and blades radiating from the peripheral wall of said hub.

In testimony whereof ll afiix my signature.

ALEXANDER BOCKSRUKER. 

